Invertebrates Flashcards

Question

what are the two types of metamorphosis in crustaceans

Answer 1

Two strategies are followed by various groups of crustaceans. A group is either "direct developers" that emerge from the egg fully formed and only increase in size as they mature, or they exhibit anamorphic growth. In anamorphic growth the morphology of the individual that emerges from the egg changes with each molt. Usually the changes involve adding segments and appendages as well as increasing in overall size. Some animals show much more dramatic changes as they metamorphose, like those seen in the stomatopod . In anamorphic growth, the larvae often look nothing like the adult.

Answer 2

stone fly fresh water shrimp

Answer 3

more fossil fuels being burnt for heat and power more food being grown land taken over for industry and housing. As a result there has been an increase in levels of water pollution. Nitrate fertilisers are very soluble in water and are easily washed off fields by the rain and then into rivers and reservoirs. Because nitrates are all soluble they cannot easily be removed from the water. Pesticides used by farmers to kill weeds or insects may be washed or blown into streams and rivers. Sulfur dioxide in the air can dissolve in water to form an acidic solution eutrophication: A major problem with the use of fertilisers occurs when they're washed off the land by rainwater into rivers and lakes. The resulting increase of nitrate or phosphate in the water encourages algae growth, which forms a bloom over the water surface. This prevents sunlight reaching other water plants, which then die. Bacteria break down the dead plants and use up the oxygen in the water so the lake may be left completely lifeless.

Answer 4

gastropoda (snails and slugs) Cephalopoda ( octopuses, squid, and cuttlefish; and Nautiloidea) Polyplacophora (chitins) Bivalvia (clams, oysters, cockles, musssels, scallops)

Answer 5

Different species of aquatic invertebrates can survive in polluted water, while others cannot. As such, scientists often take a sample of the invertebrates living in a water source and use the species in the sample to assess the level of pollution in the water. A sample with invertebrates like fresh water shrimp and mayfly larva indicates clean water, because these species have very low tolerance for any pollution. If scientists find water with many rat-tailed maggots (aquatic larvae of droneflies found throughout the uk) or sludge worms, however, they can be sure that the water is highly polluted because these species survive well in polluted waters.

Answer 6

The orders Ephemoptera (mayflies), Plectoptera (stoneflies), and Trichoptera (caddisflies) are important bio indicators for clean water as they are highly pollution sensitive blood worms, rat tail worms, sludge worms are important polluted water indicators

Answer 7

Ctenophores are the sister group of all other animals - Nervous system components are like those of sponges- sponges might have the structural components for a nervous system but lost these cell types…so secondarily without a nervous system! - Genes for mesodermal cells present but lack other animal mesodermal gene components- may be independently evolved

Answer 8

Cnidarians are distinguished from all other animals by having cnidocytes that fire like harpoons and are used mainly to capture prey. In some species, cnidocytes can also be used as anchors. ctenophores: have colloblasts instead. Cnidocyte is also called the "stinging cell". Cnidae are used for prey capture and defense from predators. There are also morphological differences between the groups. Ctenophores are called comb jellies because many of them have 8 rows of stiffened cilia that function as paddles to propel the animal through the water. Cnidarians do not have comb rows; medusae swim by contracting and releasing the bell, in a sort of gentle jet propulsion. So while ctenophores glide smoothly through the water, medusae (cnidarians) swim with a more jerky pulse-glide-pulse-glide motion. Radial symmetry is considered an adaptation for living in the open waters of the seas because it allows the animal to encounter its environment in all directions. Although medusae and ctenophores appear to have the same kind of radial symmetry, a closer look at their respective anatomies reveals differences. Medusae have more or less truly radial symmetry. On the other hand, ctenophores such as Pleurobrachia have bi-radial symmetry. The pharynx of the animal is an elongate slit, which creates one plane of bilateral symmetry, and the plane of the two tentacles is at right angles to that of the pharynx. The pharyngeal and tentacular planes of bilateral symmetry are both superimposed over the radial symmetry produced by the 8 comb rows, hence the term "bi- radial symmetry." ctenophores do not have true muscle tissue unlike cnidarians, ctenophore muscles are Mostly myoepithelial whereas cnidarians are Mostly epitheliomuscular. cnidarians also have Two cell layers that sandwich a middle layer of jelly-like material, which is called the mesoglea and ctenophores tend to have Two or Three suggesting they can be tripoblastic. cnidarians have been said to have evolved from tripoblastic ancestors. Polymorphism refers to the occurrence of structurally and functionally more than two different types of individuals within the same organism. It is a characteristic feature of Cnidarians, particularly the polyp and medusa forms, or of zooids within colonial organisms like those in Hydrozoa. In Hydrozoans, colonial individuals arising from individuals zooids will take on separate tasks.[15] For example, in Obelia there are feeding individuals, the gastrozooids; the individuals capable of asexual reproduction only, the gonozooids, blastostyles and free-living or sexually reproducing individuals, the medusae.

Answer 9

Circulatory System An insect's blood does not flow through veins and arteries as ours does. Blood fills the whole cavity of the insect's body, and bathes all the organs and muscles. The blood is circulated by a long tube that lies just under the exoskeleton of the back. This tube extends almost the entire length of the body. The pumping part of the tube lies in the abdomen, and is called the heart. The front part of the tube extends into the head, and is called the aorta. Blood enters the tube through little openings, called ostia, along the sides. The openings have valves that allow blood to enter the tube, but not to flow out. As the heart contracts, the blood is forced along the tube and out through the aorta. The blood first bathes the brain, and then flows to other parts of the body. It then re-enters the tube through the ostia. Unlike our blood, an insect's blood has little to do with bringing oxygen to the cells. Insect blood is greenish, yellowish, or colorless. Few insects have red blood. Respiratory System An insect breathes by means of tiny holes, called spiracles, along the sides of its body. Each hole leads into a large tube called a trachea. The large tubes divide into small tubes, which, in turn, divide into still smaller tubes that branch out to all the cells of the body. This system of tubes carries oxygen to the cells and takes away carbon dioxide. Nervous System consists of a brain, located in the head, and two nerve cords that lie side by side along the floor of the thorax and abdomen. The brain receives information from the eyes and antennae, and controls the insect's body activities as a whole. Another nerve center in the head is connected to the brain and controls the insect's mouth parts. Each of the two nerve cords contains a cluster of nerve cells, called a ganglion, in each segment of the thorax and abdomen. The two ganglia in each segment are fused and form a sort of little brain that controls the activities of that segment. The ganglia often can work without the brain. For example, many insects that have had their heads cut off can still walk, mate, and lay eggs. In some insects, the three pairs of ganglia in the thorax are fused into one. Various pairs of ganglia in the abdomen are also fused in many insects. Muscular System is made up of several hundred to a few thousand small but very strong muscles. Grasshoppers have about 900 muscles, and caterpillars have from 2,000 to 4,000. By contrast, man has fewer than 700 muscles. Many insects can lift or pull an object 20 or more times heavier than the weight of their bodies. Few men can lift a weight heavier than the weight of their bodies. Digestive System of an insect consists basically of a long tube that extends from the mouth to the anus. The tube has three main divisions: (1) the foregut; (2) the midgut, or stomach; (3) the hindgut, or intestine. After food has been chewed or sucked up by the mouth parts, it enters the foregut through the mouth. The food moves along the tube until it reaches an enlarged area called the crop, where it is temporarily stored and partly digested. Then the food passes into the gizzard, which has thick muscular walls that contract and grind the food into small bits. The gizzard of some insects has teeth that help break up and grind the food. The food next passes into the midgut, where most digestion takes place. Nourishing parts of the food are absorbed into the blood, and wastes and undigested parts move into the hindgut. Insects have a system of 2 to over 150 malpighian tubes attached to the digestive system where the midgut and hindgut join. The tubes float in the blood and absorb waste materials, which then pass through the tubes into the hindgut. All wastes and extra water that enter the hindgut leave the body through the anus. Reproductive System Most insects reproduce sexually. That is, a new individual can be created only after a female sex cell (egg) has united with a male sex cell (sperm). The reproductive organs are in the abdomen. Females have two organs, called ovaries, in which eggs develop. A tube called an oviduct carries the eggs away from each ovary. The two oviducts join and form a single tube that opens near the tip of the abdomen. Male insects have two organs, called testes, that produce sperm. A tube carries the sperm from each testis. The two tubes unite and form a single tube that extends to the outside of the abdomen.

Answer 10

Most species of Scyphozoa have two life history phases, including the planktonic medusa or jellyfish form, which is most evident in the warm summer months, and an inconspicuous, but longer-lived, bottom-dwelling polyp, which seasonally gives rise to new medusae. although both classes contain species that undergo bioluminescence using lucerfin, some species of deep sea jellyfish have adapted to become entirely pigmented in red or orange whereas only one species of ctenophore can partially pigment itself. scyphozoa (jellyfish): Why would they be red instead of black to blend in with the dark water? Red cannot be seen in dark water (deeper than 200 meters), so there's no greater protection from black than red. But red is preferred to black because pigment is easier for animals to produce. Some deep sea jellies just have dark red guts, possibly serving to mask luminescent prey from other larger predators with eyes. The gut of the deep-sea genus Bathocyroe (ctenophore) is red, which hides the bioluminescence of copepods it has swallowed. scyphozoans: They have limited control over movement, but can use their hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive Scyphozoans usually display a four-part symmetry and have an internal gelatinous material called mesoglea, which provides the same structural integrity as a skeleton. The mesoglea includes mobile amoeboid cells originating from the epidermis whereas ctenophores display radially symmetrical which means it is symmetrical around a central axis. Scyphomedusae lack a vellum, which is a circular membrane beneath the umbrella that helps propels the (usually smaller) Hydromedusae through the water. However, a ring of muscle fibres is present within the mesoglea around the rim of the dome, and the jellyfish swims by alternately contracting and relaxing these muscles

Answer 11

Reproduction in invertebrates differs depending on species. Asexual reproduction (having no sex or sexual organs) is quite common, however, sexual reproduction is more typical. Hermaphrodites are common in invertebrates, this means that both male and female sexual organs are present in one individual. In single sex species, where only one sexual organ is present, males and females do not have to make contact to reproduce as fertilization can occur externally. Following reproduction, most invertebrates change shape and appearance by going through a process called metamorphosis whereby adults and young have different lifestyles including how and what they feed upon.

Answer 12

Mitochondrial genome of Trichoplax adhaerens supports Placozoa as the basal lower metazoan phylum Trichoplax has the smallest genome out of any known animal, with only 50 megabases of DNA, and 6 chromosomes. The sequencing of the Trichoplax genome is currently underway. It is suspected that it may be related to cnidarians and ctenophores. Some recent molecular studies suggested that Trichoplax may have split from the rest of animals after sponges and cnidarians, however a metazoan with the simplest known body plan of any animal, possessing no organs, no basal membrane, and only four different somatic cell types. Our analysis shows that the Trichoplax mitochondrion contains the largest known metazoan mtDNA genome at 43,079 bp, more than twice the size of the typical metazoan mtDNA. The mitochondrion’s size is due to numerous intragenic spacers, several introns and ORFs of unknown function, and protein-coding regions that are generally larger than those found in other animals. Not only does the Trichoplax mtDNA have characteristics of the mitochondrial genomes of known metazoan outgroups, such as chytrid fungi and choanoflagellates, but, more importantly, it shares derived features unique to the Metazoa. Phylogenetic analyses of mitochondrial proteins provide strong support for the placement of the phylum Placozoa at the root of the Metazoa. this is most likely to be the basal metazoan over Ediacaran fauna which relies soley on morphology In 2006, Dellaporta et al reported the complete mitochondrial genome sequence of Tricoplax and demonstrated that it is the most basal known living metazoan phylum, branching off even earlier than cnidarians (jellyfish and corals). Cnidarians may have evolved from an organism as simple as Tricoplax.

Answer 13

ctene: a locomotor organ consisting of a row of strong cilia whose bases are fused

Answer 14

gastropoda (snails and slugs) Cephalopoda ( octopuses, squid, and cuttlefish; and Nautiloidea) Polyplacophora (chitins) Bivalvia (clams, oysters, cockles, musssels, scallops) Monoplacophora (molluscs with a cap-like shell) Scaphopoda (tusk shell)

Answer 15

sexual: Echinoderms become sexually mature after approximately two to three years, depending on the species and the environmental conditions. They are nearly all gonochoric, though a few species are hermaphroditic. The eggs and sperm cells are typically released into open water, where fertilization takes place. The release of sperm and eggs is synchronised in some species, usually with regard to the lunar cycle. In other species, individuals may aggregate during the reproductive season, thereby increasing the likelihood of successful fertilisation. Internal fertilisation has currently been observed in three species of sea star, three brittle stars and a deep water sea cucumber. Even at abyssal depths, where no light penetrates, synchronisation of reproductive activity in echinoderms is surprisingly frequent asexually: In certain other asterozoans, the adults reproduce asexually for a while before they mature after which time they reproduce sexually. In most of these species, asexual reproduction is by transverse fission with the disc splitting in two. Regrowth of both the lost disc area and the missing arms occur[41][52] so that an individual may have arms of varying lengths. Though in most species at least part of the disc is needed for complete regeneration, in a few species of sea stars, a single severed arm can grow into a complete individual over a period of several months. Asexual reproduction by transverse fission has also been observed in adult sea cucumbers. Holothuria parvula uses this method frequently, an individual splitting into two a little in front of the midpoint. The two halves each regenerate their missing organs over a period of several months but the missing genital organs are often very slow to develop Asexual reproduction in the planktonic larvae of species such as and brittle stars, sea cucumber, sand dollar and sea urchin.occurs through numerous modes. They may autotomise parts that develop into secondary larvae, grow buds or undergo paratomy. The parts that are autotomised or the buds may develop directly into fully formed larvae or may develop through a gastrula or even a blastula stage

Answer 16

habitat - very diverse, gardens, sea, desert, mountains, parasitic niches etc Gastropods can be accidentally transferred from one habitat to another by other animals, e.g. by birds. The smallest bird species reported to carry a gastropod was a great tit (Parus major), as a hairy snail Trochulus hispidus was found in the plumage of a wintering great tit in Poland in 2010 The gastropod’s most identifiable physical characteristic is its “torsion” process. During its growth and development, the internal organs rotate 180°, so that the anus migrates to just above the gastropod’s head The gastropod can have either two or four sensory tentacles. Most gastropods have simple eye-spots at the tip of the tentacles that can only detect light and dark.

Answer 17

Radula, a rasping "tongue" with chitinous teeth, shared with Broad, muscular foot called a propodium found in bivalves although the morphology differs as bivalve feet are pointed for digging not for moving

Answer 18

- gut is much reduced in some species - no mouth opening in some species as they feed only as larvae absorbing nutrients from the hosts body wall e.g. horse hair worms - In some nematodes (e.g. Ascaris) chitinous jaws are present inside mouth which helps them to anchor with the wall of gut

Answer 19

flatworm parasites likely evolved from a single speciation event and continued with adaptive radiation due to preparasitism traits making it very sucessful(maule, 2006)

Answer 20

All spiders produce silk, a thin, strong protein strand extruded by the spider from spinnerets, Many species use it to trap insects in webs, although there are many species that hunt freely. Silk can be used to aid in climbing, form smooth walls for burrows, build egg sacs, wrap prey, temporarily hold sperm, and even fly, among other applications. all spiders except for 2 families can inject venom into prey to immobilise it or defend from predators

Answer 21

``` Spend up to one year in the stream. • Have little mobility • Generally abundant • Primary food source for many fish • Good indicators of localized conditions ```

Answer 22

Hypothesis 1. Arthropoda is the sister group of the Annelida, which together comprise the Articulata. Mollusca is the sister group of the Articulata. • Hypothesis 2. Annelida and Mollusca are sister groups, which together comprise the Eutrochozoa. Arthropoda is the sister group of the Eutrochozoa. • Hypothesis 3. Arthropoda and Mollusca are sister groups and Annelida is the sister group of the Arthropoda + Mollusca clade. • These 3 phylogenetic hypotheses can be “tested” by mapping apomorphic characters on to cladograms and counting up the number of steps required. By the principle of parsimony, the hypothesis with the least number of steps is more likely to be true. • Parsimony analysis provides equal support for hypothesis 1 (Articulata) and hypothesis 2 (Eutrochozoa). In each instance, a minimum of three evolutionary changes are required. Hypothesis 3 requires at least four evolutionary changes and is therefore less parsimonous.

Answer 23

Molluscs and annelids are more closely related to each other than either is to arthropods. This means that segmentation as observed in rthropods and annelids is homoplastic and not homologous. In contrast, the trochophore larvae present in molluscs and annelids is probably a true homology. having more characters in a phylogenetic analysis does not necessarily make things easier. More characters may mean more chances for conflicts in terms of the hierarchical nesting of them. Molecular characters may improve phylogenetic analysis, but errors may occur when the rates of evolution are vastly different in different lineages (e.g., the long branch attraction problem, a problem seen in nematodes).

Answer 24

Lophotrochozoans vs. Ecdysozoans Genome analysis, especially the analysis of •18S rRNA genes and •HOX genes supports a major division of the Protostomia into two superphyla: •Lophotrochozoans and •Ecdysozoans Lophotrochozoans Their name was created from the names of formerly-separated groups that have now been joined in a single clade on the basis of the similarities of their genomes: •They all share a cluster of HOX genes quite different from those found in the ecdysozoans (and deuterostomes). •They share similar sequences in their 18S rRNA genes. The clade contains a number of phyla of which we shall examine only 3. •flatworms (Platyhelminthes), •annelids (Annelida), and •mollusks (Mollusca). Ecdysozoans All the members of this clade •grow by periodically molting — shedding their skin or exoskeleton; •share a unique pattern of HOX genes, e.g. Ubx and Abd-B. The clade includes a number of phyla of which we shall examine 2: •the nematodes and the •arthropods. The Deuterostomes In addition to the features listed above, the deuterostomes have (or had) gill slits. (The echinoderms have lost the gill slits of their ancestors.) Echinoderms (Phylum Echinodermata) Characteristics: •radial symmetry. HOWEVER, their larvae have bilateral symmetry so the echinoderms probably evolved from bilaterally symmetrical ancestors and properly belong in the Bilateria. •water vascular system. Seawater is taken into a system of canals and is used to extend the many tube feet. These have suckers on their tips and aid the animal in attaching itself to solid surfaces. •no gill slits •About 6,000 species — all of them marine

Answer 25

trichoplax adhaerans (placozoans), Trichoplax has the smallest genome out of any known animal, with only 50 megabases of DNA, and 6 chromosomes and thought to be related to cnidarians and ctenophores. Some recent molecular studies suggested that Trichoplax may have split from the rest of animals after sponges and cnidarians

Answer 26

cnidarians (jellyfish and relatives), porifera (sponges), ctenophores (comb jellies), placozoans (the only animal phyla with a single species, Trichoplax adhaerens) and members of the large clade Bilateria

Answer 27

draculiasis/guinea worm disease trichnosis caused by trichinella spiralis lymphatic filiarasis caused by wucheria bancrofti

Answer 28

cnidarians were found to have split off earlier than sponges suggesting that sponges are not the most basal of all basal metazoans Although it was long suspected that sponges were the most basal of all major groups of metazoans, a genetic study from 2007 determined that, in fact, cnidarians split off from other metazoans earlier than the sponges. This is quite a surprise, as cnidarians are clearly more complex than sponges. The finding demonstrates that morphology (appearance) cannot be used as a yardstick for how early an organism split off from the others, as some animals become less complex over time, not more.

Answer 29

order of arachnids that live in the top layers of soil Schizomids present the prosoma covered by a large protopeltidium and smaller, paired, mesopeltidia and metapeltidia. There are no eyes. The opisthosoma is a smooth oval of 12 recognisable somites. The first is reduced and forms the pedicel. The last three are much constricted, forming the pygidium. The last somite bears the flagellum, which in this order is short and consists of not more than four segments. The name means "split or cleaved middle", referring to the way the cephalothorax is divided into two separate plates. Like the Thelyphonida, Amblypygi, and Solifugae, the schizomids use only six legs for walking, having modified their first two legs to serve as sensory organs. They also have large well-developed pedipalps (pincers) just behind the sensory legs.

Answer 30

both have sexual and asexual reproduction both can release eggs and sperm into the ocean to fertilise although this mostly occurs in echinoderms. both can be hermaphrodites e.g. brittle starfish (echinoderm) however in these species direct development without passing through a bilateral larval stage usually takes place which doesn't occur in poferia. some echinoderms (brittle star, sea cucumber, sand dollar) reproduces asexually through budding. They may autotomise parts that develop into secondary larvae, grow buds or undergo paratomy. The parts that are autotomised or the buds may develop directly into fully formed larvae or may develop through a gastrula or even a blastula stage

Answer 31

small arthropods with a flat, pear-shaped body and pincers that resemble those of scorpions The opisthosoma is made up of twelve segments, each guarded by plate-like tergites above and sternites below. The abdomen is short and rounded at the rear, rather than extending into a segmented tail and stinger like true scorpions They may have two, four or no eyes. They have two very long pedipalps with palpal chelae (pincers) that strongly resemble the pincers found on a scorpion. The pedipalps generally consist of an immobile "hand" and "finger", with a separate movable finger controlled by an adductor muscle. A venom gland and duct are usually located in the mobile finger; the poison is used to capture and immobilise the pseudoscorpion's prey. During digestion, pseudoscorpions pour a mildly corrosive fluid over the prey, then ingest the liquefied remains. Pseudoscorpions spin silk from a gland in their jaws to make disk-shaped cocoons for mating, molting, or waiting out cold weather. Another trait they share with their closest relatives, the spiders, is breathing through spiracles. Most spiders have one pair of spiracles, and one of book lungs, but pseudoscorpions do not have book lungs.

Answer 32

These worms ingest sediments, selectively digest bacteria, and absorb molecules through their body walls. The worms can survive with little oxygen by waving hemoglobin-rich tail ends to exploit all available oxygen, and can exchange carbon dioxide and oxygen through their thin skins, in a manner similar to frogs. They can also survive in areas heavily polluted with organic matter that almost no other species can endure. By forming a protective cyst and lowering its metabolic rate, T. tubifex can survive drought and food shortage.

Answer 33

Chitons have a dorsal shell, which is composed of eight separate shell plates or valves. These plates overlap somewhat at the front and back edges, and yet articulate well with one another. Because of this, although the plates provide good protection for impacts from above, they nonetheless permit the chiton to flex upward when needed for locomotion over uneven surfaces, and also allow the animal to slowly curl up into a ball when it is dislodged from the underlying surface.[7] The shell plates are surrounded by a structure known as a girdle.

Answer 34

Several animal phyla are recognized for their lack of bilateral symmetry, and are thought to have diverged from other animals early in evolution. Among these, the sponges (Porifera) were long thought to have diverged first, representing the oldest animal phylum.[55] They lack the complex organization found in most other phyla.[56] Their cells are differentiated, but in most cases not organized into distinct tissues Among the other phyla, the Ctenophora and the Cnidaria, are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus Both have distinct tissues, but they are not organized into organs.[68] There are only two main germ layers, the ectoderm and endoderm, with only scattered cells between them. As such, these animals are sometimes called diploblastic.[69] The tiny placozoans are similar, but they do not have a permanent digestive chamber.

Answer 35

two of the most successful animal phyla, the Mollusca and Annelida. mollusca is the second-largest animal phylum by number of described species, includes animals such as snails, clams, and squids, and the latter comprises the segmented worms, such as earthworms and leeches. These two groups have long been considered close relatives because of the common presence of trochophore larvae, but the annelids were considered closer to the arthropods because they are both segmented.[44] Now, this is generally considered convergent evolution, owing to many morphological and genetic differences between the two phyla Segmented worms and mollusks evolved in the ocean approximately 550 million years ago. They are closely related based on embryology. The development of excretory systems and eyes occur first in these groups. Characteristics shared with the Annelida include pelagic larvae (trochophore) with one or more bands of locomotory cilia located equatorially (near the mouth) and formed before gastrulation, pelagic larva with para- or circumanal ciliary tuft, and paired excretory organs and ducts that open externally (nephridiopores).

Answer 36

Acari – mites and ticks Amblypygi – "blunt rump" tail-less whip scorpions with front legs modified into whip-like sensory structures Araneae – spiders Opiliones – phalangids, harvestmen or daddy-long-legs (6,300 species) Pseudoscorpionida – pseudoscorpions (3,000 species) Ricinulei – ricinuleids, hooded tickspiders (60 species) Scorpiones – scorpions (2,000 species) Solifugae – solpugids, windscorpions, sun spiders or camel spiders (900 species)

Answer 37

cubozoa are distinguished by their cube-shaped medusa cubozoa have an extremely potent poison allowing them to efficiently kill their prey whereas comb jellies (ctenophores) do not possess any poison. Upon touch, a spiral filament automatically bursts out of colloblast cells that releases the sticky glue. Once an item is stuck, the comb jelly reels in its tentacle and brings the food into its mouth.

Answer 38

hooded tickspiders Their most notable feature is a "hood" that can be raised and lowered over the head; when lowered, it covers the mouth and the chelicerae. Ricinulei have no eyes. The pedipalps end in pincers that are small relative to their bodies, when compared to those of the related orders of scorpions and pseudoscorpions. The heavy-bodied abdomen forms a narrow pedicel, or waist, where it attaches to the prosoma. In males, the third pair of legs are modified to form copulatory organs. Malpighian tubules and a pair of coxal glands make up the excretory system. They have no lungs, as gas exchange takes place through the trachea. ricinulei require moisture to survive

Answer 39

Radula, a rasping "tongue" with chitinous teeth, shared with Broad, muscular foot

Answer 40

Three physical features separate insects from other arthropods: they have a body divided into three regions (head, thorax, and abdomen), have three pairs of legs, and mouthparts located outside of the head capsule. It is this position of the mouthparts which divides them from their closest relatives, the non-insect hexapods

Answer 41

poferia reproduce asexually and sexually. Sponges have three asexual methods of reproduction: after fragmentation; by budding; and by producing gemmules. Fragments of sponges may be detached by currents or waves. They use the mobility of their pinacocytes and choanocytes and reshaping of the mesohyl to re-attach themselves to a suitable surface and then rebuild themselves as small but functional sponges over the course of several days. The same capabilities enable sponges to regenerate when shredded. HOWEVER A sponge fragment can only regenerate if it contains both collencytes to produce mesohyl and archeocytes to produce all the other cell types. Gemmules are "survival pods" which a few marine sponges and many freshwater species produce by the thousands when dying and which some, mainly freshwater species, regularly produce in autumn. Spongocytes make gemmules by wrapping shells of spongin, often reinforced with spicules, round clusters of archeocytes that are full of nutrients which become dormant. When a gemmule germinates, the archeocytes round the outside of the cluster transform into pinacocytes, a membrane over a pore in the shell bursts, the cluster of cells slowly emerges, and most of the remaining archeocytes transform into other cell types needed to make a functioning sponge. Gemmules from the same species but different individuals can join forces to form one sponge sexually: Most sponges are hermaphrodites (function as both sexes simultaneously), although sponges have no gonads (reproductive organs). Sperm are produced by choanocytes or entire choanocyte chambers that sink into the mesohyl and form spermatic cysts while eggs are formed by transformation of archeocytes, or of choanocytes in some species. During spawning, sperm burst out of their cysts and are expelled via the osculum. If they contact another sponge of the same species, the water flow carries them to choanocytes that engulf them but, instead of digesting them, metamorphose to an ameboid form and carry the sperm through the mesohyl to eggs A few species release fertilized eggs into the water, but most retain the eggs until they hatch. There are four types of larvae, but all are balls of cells with an outer layer of cells whose flagellae or cilia enable the larvae to move. After swimming for a few days the larvae sink and crawl until they find a place to settle. Most of the cells transform into archeocytes and then into the types appropriate for their locations in a miniature adult sponge

Answer 42

1. it would divide all species into vertebrates and non vertebrates which is very vague, it is not based on any clear biologically homologous trait, it is as vague as grouping all species with tails vs non tails or humans and non humans 2. vertebrates are an evolutionary trait whereas all inverts are grouped together 3."you shouldn't define something by it not being defined by another classification" 4. there are 34 animal phyla and 33.5 of these are invertebrates, 25 of which are aquatic, 2 are predominantly terrestrial 5. discuss the different types of major inverts and how they differ from each other, define an invert and define a vertebrate in the intro 6. discuss more suitable divisions - presence of a notochord: flexible rod made out of a material similar to cartilage. The notochord is the defining feature of Chordates, and was present throughout life in many of the earliest chordates. However, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps body plan - body plans and symmetry would divide species into more specific groups as most multicellular organisms exhibit some form of symmetry, whether radial, bilateral, or spherical. A minority, however, exhibit no symmetry The term invertebrates is not always precise among non-biologists since it does not accurately describe a taxon in the same way that Arthropoda, Vertebrata or Manidae do. Each of these terms describes a valid taxon, phylum, subphylum or family. invertebrates is a term of convenience rather than a taxon term. ``` most notable inverts: Insects Molluscs Crustaceans Corals Arachnids Velvet worms Horseshoe crabs ``` Invertebrates are animals without a vertebral column. This has led to the conclusion that invertebrates are a group that deviates from the normal, vertebrates. This has been said to be because researchers in the past, such as Lamarck, viewed vertebrates as a "standard": in Lamarck's theory of evolution, he believed that characteristics acquired through the evolutionary process involved not only survival, but also progression toward a "higher form", to which humans and vertebrates were closer than invertebrates were. It's also possible that some humans believe that, they themselves being vertebrates, the group deserves more attention than invertebrates.[53] In any event, in the 1968 edition of Invertebrate Zoology, it is noted that "division of the Animal Kingdom into vertebrates and invertebrates is artificial and reflects human bias in favor of man's own relatives."

Answer 43

There are many thousands of species of sea snails and sea slugs, as well as freshwater snails, freshwater limpets, land snails and land slugs.

Answer 44

Cnidarians were formerly grouped with ctenophores in the phylum Coelenterata, but increasing awareness of their differences caused them to be placed in separate phyla. Cnidarians are classified into four main groups: the almost wholly sessile Anthozoa (sea anemones, corals, sea pens); swimming Scyphozoa (jellyfish); Cubozoa (box jellies); and Hydrozoa,

Answer 45

Each larva is equipped with an extendible tail called a 'siphon'. This tail, which can extend to about 5cm (2 inches), is used as a snorkel to breath air from the surface of the liquid while the larva feeds below.

Answer 46

the higher the bmwp the less tolerant to pollution

Answer 47

The biological monitoring working party (BMWP) is a procedure for measuring water quality using families of macroinvertebrates as biological indicators.

Answer 48

In the case of BMWP/Organic pollution rankings, the presence of mayflies or stoneflies for instance indicate the cleanest waterways and are given a tolerance score of 10.[1] The lowest scoring invertebrates are worms (Oligochaeta) which score 1.

Answer 49

although segmentation allows annelids such as earthworms to move underground whilst simultaneously feeding, this movement is extremely slow and leaves them vulnerable to predation by birds and other fast moving predators or at risk from drowning from being too slow to migrate towards the surface or escape from puddles on the surface when it rains segmentation allows for specialisation to different niches however this can lead to an animal becoming too specialised to its environment and unable to survive well outside of it as with the above example

Answer 50

allows for higher mobility and greater movement but this leaves gaps between segments not covered by an exoskeleton. this vulnerability in protection comes at the cost of a more efficient range of movement t catch prey e.g. centipedes

Answer 51

intermoult - general day to day activities when growth occurs. proecdydsis - preparation phase when feeding stops and new cuticle formation begins apolysis - the seperation of the exoskeleton from the underlying epidermal cells, inactivity is caused by the secretion of fluid frm the moutling glands of the epidermal layer and loosening of the cuticle. ecdydsis - fluid secretions activate, increased blood pressure and retained water helps the individual to split and push the old exoskeleton off. a new layer is then secreted as the old layer is digested. post ecdysis - the skin becomes sclerotised and excess water and air is eliminated to allow the soft tissue to shrink back.

Answer 52

it is the molting of the cuticle in invertebrates. this cuticle forms an exoskeleton which cannot grow with the body, during ecdysis a newer larger exoskeleton forms and hardens within a few hours. ecydysis occurs in species from the clade ecysozoans featuring arthropods, nematodes, velvet worms, horse hair worms and tarigardes.

Answer 53

it is the serial repetition of similar organs, tissues, cells or body cavities along the anterior-posterior axis of bilaterally symmetrical animals there are three types of segmented animals annelids arthropods vertebrates

Answer 54

- without segmentation they would lack a sophisticated method of movement with soil - segmentation allows more complex activities and the use of different segments for different functions such as locomotion - e.g. bristle worms use heteromeric segmentation to move - segmentation allows for a greater degree of variety amongst all animals in terms of body plans. this lets animals become differently shaped to fill available niched and habitats - segmentation is not just external, it allows the bodys internal systems to be divided into different sections e.g. digestive, nervous, circulatory.

Answer 55

gastropods, chitons (polyplacophora) and gastropods have a radula, a rasping tongue structure to scrape and cut food before it is digested. bivalves filter feed instead and dont have a radula gastropods and bivalves: the foot and other soft parts of the body can usually be completely withdrawn into the shell and the opening covered by a permanent plate called the operculum

Answer 56

creation of pearls to get rid of irritants, e.g. a grain of sand enters and causes irritation, creates a pearl around it to make it less painful.

Answer 57

Cephalopods, like most mollusks, have a mantle, a mantle cavity, a radula, and a U-shaped digestive tract

Answer 58

the most obvious difference between most cephalopods and other mollusks is the apparent lack of a shell. Octopuses do not have shells at all, while squids have a small internal shell. (Nautiluses, which are found in the South Pacific and Indian oceans, are the only cephalopods with an external shell

Answer 59

annelids: largely segmented bodies, each segment contains elements of different body systems (homomeric) essential for life e.g. digestive arthopods: consist of series of segments that replicate each other in function (homomeric), segmentation tends to occur in larger body plans.

Invertebrates Flashcards

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